The invention relates to an information recording media for promptly and accurately storing a large amount of information and, more particularly, to an information recording media for use as an information recording disk having high performance and high reliability and a magnetic storage apparatus and an magneto-optical storage apparatus using such a media.
The progress of the recent advanced information society is remarkable and a multimedia in which information of various formats has been integrated is being rapidly spread. As an information recording apparatus which supports it, there are a magnetic recording disk drive and a magneto-optical recording disk drive. At present, in the magnetic recording disk drive, miniaturization is being realized while improving a recording density. In association with it, the realization of a low price of the disk drive is being rapidly progressed. To realize a high density of the magnetic recording disk, techniques (1) to shorten a distance between the magnetic recording disk and a magnetic head, (2) to increase coercivity of a magnetic recording media, (3) to devise a signal processing method, and the like are indispensable techniques. Among them, in the magnetic recording media, an increase in coercivity is indispensable to realize a high density recording. In addition to it, to realize a recording density exceeding 20 Gb/in2, a unit in which a magnetization reversal occurs has to be reduced. For this purpose, it is necessary to microfine a size of magnetic crystal grain. As a method of realizing it, a method whereby a shield layer is provided under a magnetic layer has been proposed. As an example of such a method, U.S. Pat. No. 4,652,499 can be mentioned.
In a magneto-optical recording disk drive for writing, reading, or erasing by using a laser beam, it is effective to form a micro magnetic domain by using a laser beam of a short wavelength. In this case, since a Kerr effect shown by an amorphous alloy of a rare earth element and an iron group element as a recording media decreases in association with a decrease in wavelength of the laser beam, a read output to noise ratio (S/N) decreases and there is a case where a stable information recording cannot be performed. To solve such a problem, an artificial lattice layer obtained by alternately laminating Pt and Co showing a large Kerr effect even in a short wavelength region of 400 nm or less has been proposed. As an example of such a layer, JP-A-1-251356 can be mentioned.
In the above related art, first, in the magnetic recording disks, there is a limitation in a grain-size distribution control of crystal grain of an information recording magnetic layer by a shield layer and there is a case where both micro grain and enlarged grain exist. In case of reversing the magnetization and recording information, the micro grain is influenced by a leakage magnetic field from the peripheral magnetic crystal grain and the enlarged grain causes an interaction with the peripheral magnetic crystal grain to the contrary. Therefore, when an ultra-high density magnetic recording exceeding 20 GB/inch2 is performed, there is a case where the stable recording cannot be performed. This problem also similarly occurs in a magnetic recording disk having a magnetic layer for longitudinal magnetic recording and in a magnetic recording disk having a magnetic layer for perpendicular magnetic recording of the Coxe2x80x94Cr system.
In the magneto-optical recording, if the artificial lattice layer obtained by alternately laminating Pt and Co is used as a recording layer, although a large Kerr rotational angle is obtained even in the short wavelength region of 400 nm or less, a moving speed of a magnetic wall is high. Particularly, in case of performing a mark length recording, it becomes a cause of a jitter and the stable writing or read-back cannot be performed.
In consideration of the problems of such a related art, it is an object of the invention to provide an information recording media suitable for performing an ultra-high density magnetic recording, namely, a magnetic recording media or magneto-optical recording media. Another object of the invention is to provide a magnetic storage apparatus and a magneto-optical storage apparatus which are suitable for an ultra-high density magnetic recording.
The above objects are accomplished by controlling a distribution of a magnetization reversal size of a magnetic layer in an information recording media. The above objects are also accomplished by providing a portion serving as a pinning site of the movement of a magnetic wall for a magnetic layer in an information recording media.
That is, an information recording media according to the invention is characterized in that: it includes a substrate, an inorganic compound layer formed on the substrate, and a magnetic layer formed on the inorganic compound layer; the inorganic compound layer is a layer in which an oxide of at least one kind selected from silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, and zinc oxide exists in an amorphous state at a grain boundary of crystal grain of an oxide of at least one kind selected from cobalt oxide, iron oxide, and nickel oxide; and the magnetic layer is an artificial lattice multilayer obtained by alternately laminating a Co layer or an alloy layer consisting of Co as a main phase and a metal element layer of at least one kind selected from Pt and Pd. As an alloy consisting of Co as a main phase, for example, Coxe2x80x94Cr, Coxe2x80x94Crxe2x80x94Pt, or Coxe2x80x94Crxe2x80x94Ta can be used.
The inorganic compound layer has a honeycomb structure in which hexagonal crystal grains are two-dimensionally and regularly arranged when it is seen from the direction that is perpendicular to a layer surface. It is preferable that the crystal grain in the inorganic compound layer has a grain-size distribution in which a standard deviation of the grain-size distribution of the crystal grain when it is seen in the in-plane direction is equal to or less than 10% of an average grain size. It is also desirable that a thickness of inorganic compound layer lies within a range from 10 nm or more to 100 nm or less. A lower limit of the layer thickness is equal to a thickness at which the inorganic compound layer can be stably formed and an upper limit is determined by an internal stress which the inorganic compound layer has.
The magnetic layer has the same crystal shape as that of the crystal grain in the inorganic compound layer and is formed by epitaxially growing crystal grain of the magnetic layer in a column shape onto a crystal phase of the inorganic compound layer. Thus, the crystal grain of the magnetic layer exists in correspondence to the crystal grain in the inorganic compound layer and amorphous or polycrystalline magnetic crystal grain exists in correspondence to a grain boundary phase of the inorganic compound layer. To form the magnetic layer of the artificial lattice multilayer structure onto the inorganic compound layer, it is preferable to use a structure in which a Co layer is used as a first layer, the Co layer of the first layer is epitaxially grown from the crystal grain of the inorganic compound layer, and Co which is formed in the grain boundary phase is polycrystalline or amorphous.
A change in magnetic properties occurs in the magnetic layer in the layer surface direction due to a difference of the crystalline structure. That is, as for the magnetic layer, the magnetic properties of at least one of the magnetic anisotropy, coercivity, and saturation magnetization differs in dependence on the portion which was epitaxially grown on the crystal phase of the inorganic compound layer and the portion grown on the grain boundary phase. Thus, the moving speed of the magnetic wall can be controlled by setting a pinning site of the magnetic wall movement in the amorphous or polycrystalline region. By reflecting the structure of the inorganic compound layer of the lower layer and providing a portion of a different crystalline structure into the magnetic layer as mentioned above, a distribution of the magnetic properties can be formed in the magnetic layer. If the distribution of the magnetic properties was formed in the magnetic layer, since the moving speed of the magnetic wall in the magnetic domain which is formed in the magnetic layer can be controlled in case of recording information, the size of formed magnetic domain or the precision of the position can be improved.
The information recording media according to the invention can be used as a magnetic recording media for the magnetic storage apparatus or a magneto-optical recording media for the magneto-optical storage apparatus. The substrate can be made of an organic compound, an inorganic compound, or a metal. A glass substrate is suitable as a substrate made of an inorganic compound. A substrate made of Al or an Al alloy can be used as a substrate made of a metal. An NiP layer can be also formed on the substrate made of an inorganic compound or metal. A high molecular material such as polycarbonate, polymethyl methacrylate (PMMA), amorphous polyolefin (APO), epoxy resin, or the like can be used as a substrate made of an organic compound.
According to the invention, there is provided a magnetic storage apparatus comprising: a magnetic recording media; a magnetic recording medium driver for driving the magnetic recording media; a magnetic head for performing a writing and a read to/from the magnetic recording media; a magnetic head access system for accessing the magnetic head; and a read/write signal processing system for processing a write signal and a read signal of the magnetic head, wherein the foregoing information recording media is used as a magnetic recording media.
According to the invention, there is provided a magneto-optical storage apparatus comprising: a magneto-optical recording media; a magneto-optical recording medium driver for driving the magneto-optical recording media; an optical head for performing a writing and a read to/from the magneto-optical recording media; an optical head access system for accessing the optical head; a signal processing system for processing a write signal and a read signal of the optical head; and magnetic field applying means for applying a magnetic field to a region on the magneto-optical recording media at a place near the optical head, wherein the foregoing information recording media is used as a magneto-optical recording media.